Patch Clamp Techniques 1&2 Flashcards
What is resistance
a measure of the opposition to current flow in an electrical circuit.
What is current
Rate of flow of charged particles aka the charge transfered over time
What is voltage
The electrical potential difference - no current if voltage the same at both ends to need a difference between the ends.
E.g. 10V at one end 0V at the other, will flow towards 0V
What is ground
A point of reference - no change in voltage but different starting point e.g. 20mV instead of 0 so inside the cell was 60mV but with ground included its 40mV
What is the relationship between current resistance and flow
All rely on each other so -
V=IR
What is capacitance
The change in potential (charge)
Units - farads
What is the role of a capacitors
A capacitor stores and releases current in a circuit - can release current when no voltage if the energy is stored
What has capacitance in cells
Cell membrane
What has current in cells
Ions flowing through cell membrane
What has voltage in cells
The potential difference across the membrane
What has resistance in cells
Ion channels
Does the number of channels (resistors) in parallel effect the current
No - current spread over 1 or 20 resistors, it doesnt matter, all add up to total current
It = I1 + I2 + I3 etc
What is the relationship with conductance and resistance
Conductance is the inverse of resistance
What happens at the ion equilibrium potential
There is no net flow of ions across the membrane - it is different for different ions
What two factors allows the cell to have a membrane potential
Concentration gradient is due to ion pumps (Na/K ATPase)
Electrical potential is due to selective membrane permeability
What is the resting potential of neuron cells
- 60mV
What is the resting potential of muscle cells
- 90mV
Where is there more potassium
Inside the cell
Where is there more sodium
Outside the cell
Where is there more chloride
Outside the cell
Where is there more calcium
Outside the cell
What is the purpose of the voltage clamp
Allows the voltage across the membrane to be fixed and this allows the current flowing across that membrane to be measured.
This allowed analysis of single ion channels as allowed control of the external and internal cell environments and recorded low noise (single-channel currents)